The use of powder form titanium dioxide to produce shaped catalysts or catalyst carriers has been known for a long time. For certain applications, such as for “Claus catalysis”, the titanium dioxide shaped parts can be used directly as catalyst without the addition of further materials.
For other applications, shaped parts containing titanium dioxide are treated with active metals such as Cr, Mo, W, Fe, Ru, Os, Co, Ni, Pd, Pt, Cu, Ag, V or Zn or metal oxides thereof. In these cases, the shaped parts containing titanium dioxide serve as “catalyst carriers”. Combined processing of titanium dioxide with active materials to produce catalysts that contain titanium dioxide is also known. Thus for example, catalysts consisting of titanium dioxide, WO3 and V2O5 are used for the selective catalytic reduction of nitrogen oxides in waste gases from furnaces, refuse incineration plants, gas turbines, industrial plants and engines.
Such titanium dioxide shaped parts, which are used as catalysts or catalyst carriers for fixed bed or fluid bed systems, must have sufficient mechanical strengths, since otherwise the catalyst may disintegrate when the reactor is filled and/or it may be crushed by the gas pressure, the thermal load and dynamic stresses during the reaction, or it may be destroyed by powerful abrasive forces.
U.S. Pat. No. 4,113,660 describes a method for producing catalysts and catalyst carriers (shaped parts) with improved mechanical strengths, which consist mainly of titanium dioxide. The shaped parts are produced by subjecting titanium dioxide or a precursor thereof to a calcining process at temperatures from 200 to 800° C. in the presence of metatitanic acid sol or gel.
U.S. Pat. No. 4,388,288 describes a method for producing porous titanium dioxide catalysts/catalyst carriers in the form of shaped parts, in which amorphous or poorly crystalline titanium dioxides in powder form are mixed with water and an auxiliary shaping agent. This paste is then shaped and annealed, typically at temperatures from 200-900° C.
U.S. Pat. No. 3,919,119 describes the production of catalyst carrier with improved abrasion properties, which comprise a mixture of a titanium chelate with titanium dioxide and a gelling agent. After the mixture has been gelled, it is dried and calcined. The titanium chelate complex used is preferably diethanolamine titanate.
EP 0389041A1 describes a method for preparing titanium dioxide extrudates from a mouldable paste, wherein the method includes steps of mixing and kneading a particulate titanium dioxide with water and an alkanolamine or ammonia or an ammonia releasing compound. The extrusion and calcining of the extruded pasty strands, typically at 450-750° C., is also described. EP 0389041 only describes titanium dioxide shaped parts with specific surface areas of less than 100 m2/g that have been prepared by the addition of inorganic additives such as silica or zeolites.
Titanium dioxide-based powder form catalyst materials that have high specific surface areas and particularly which lend themselves well to the production of titanium dioxide shaped parts with high specific surface areas and have good mechanical strengths are not known in the related art.
The object of the invention is to overcome the drawbacks of the related art and to provide a catalyst precursor material on a titanium dioxide base with high specific surface area that is particularly suitable for the preparation of titanium dioxide shaped parts and at the same time has high mechanical strengths and a large specific surface area.
Now, the inventors have found that a TiO2-based catalyst precursor material in powder form that contains one or more auxiliary shaping agents and has specific surface areas of at least 150 m2/g can be used to prepare titanium dioxide shaped parts that have surprisingly good mechanical strengths and a high specific surface areas.